Despite decades of efforts to restore and protect the Great Lakes, dozens of old power plants still are allowed to kill hundreds of millions of fish each year by sucking in massive amounts of water to cool their equipment.

Records obtained by the Tribune show that staggering numbers of fish die when pulled into the screens of water intake systems so powerful that most could fill an Olympic swimming pool in less than a minute. Billions more eggs, larvae and juvenile fish that are small enough to pass through the screens are cooked to death by intense heat and high pressure inside the coal, gas and nuclear plants.

Then the water is pumped back into Lake Michigan and the other Great Lakes up to 30 degrees hotter, encouraging the growth of oxygen-depleting algae that kills fish and fouls beaches.

Known as "once-through" cooling, the process is banned at new power plants. But for nearly four decades, federal and state environmental regulators largely have ignored the issue at old plants, even as fish populations decline sharply throughout the lakes and states spend millions of taxpayer dollars to stock the waters with game fish.

Cooling intakes kill fish prized by anglers and sold in supermarkets, along with many more smaller fish and other aquatic organisms that those species depend on for food. Critics compare the outdated technology to the Bass-o-Matic, the fish-pureeing prop from an old "Saturday Night Live" sketch.

"These plants are consistent killers, plain and simple," said Frank Reynolds, a commercial fisherman on Lake Erie who since the 1970s has been showing up at public meetings with a jar of walleye larvae to draw attention to the issue. "They're trying every way they can to avoid doing something to protect the fish."

The Tribune obtained thousands of pages of industry reports documenting power plant fish kills through Freedom of Information Act requests to the eight Great Lakes states and the U.S. Environmental Protection Agency. Michigan and New York provided only limited information, while Indiana failed to respond in time to be included in this story, but the available records highlight a threat to the Great Lakes ecosystem that has largely gone unaddressed for years.

Among the findings:

•The fish killed at the Point Beach nuclear plant north of Manitowoc, Wis., reduce the yield of Lake Michigan's fisheries by an estimated 10,625 pounds a year, or about 4.5 percent of the annual commercial fishing catch by weight.

•Across Lake Michigan from Chicago, the Cook nuclear plant near Benton Harbor, Mich., kills more than 1.3 million fish annually, most of which are yellow perch. An additional 196 million eggs and other organisms die each year inside the plant's cooling system. In Waukegan, the lone Illinois power plant on the lake kills up to 5.2 million fish a year.

•On Lake Erie, the Bay Shore coal plant near Toledo, Ohio, kills 46 million adult fish and more than 2.4 billion eggs, larvae and young fish each year in the region's most prolific spawning grounds. Less than 15 miles away, the Monroe coal plant in Michigan each year kills more than 25 million fish and 499 million eggs and other organisms on the western edge of the lake.

Federal law requires new power plants to install less-destructive equipment such as cooling towers, which act like a car's radiator and draw water only to make up for what is lost through evaporation. At the Nine Mile Point nuclear plant on Lake Ontario in New York, a reactor that has a once-through cooling system killed 154,541 fish in 2007, but a second reactor with a cooling tower killed just 34,128, documents show.

Industry lawsuits have delayed the phaseout of once-through cooling at older plants. Echoing their arguments about tougher air-pollution rules, power company lobbyists say the expense would force dozens of plants to close, costing jobs and making the nation's electrical grid less reliable. Some plants have tried to reduce fish kills by building intakes offshore away from spots where fish congregate. Others have installed systems designed to deter fish with sound or air bubbles.

"It's not clear to me scientifically that there is a broad-based problem out there that needs to be fixed," said C. Richard Bozek, director of environmental policy for the Edison Electric Institute, a trade group for energy companies. "There are situations out there that need to be addressed, but those decisions should be made on a site-by-site basis."

When Congress passed the Clean Water Act in 1972, lawmakers included a provision intended to help restore the Great Lakes and other U.S. lakes and rivers by forcing polluters to significantly reduce their water withdrawals. Faced with a court order, the Obama administration in March proposed new nationwide rules that will require older power plants either to meet certain limits on fish kills or to reduce the velocity of their water intakes.

However, the EPA would leave enforcement to state officials who have allowed cooling intakes to be used with few if any limits. The proposed rules also exempt companies from installing cooling towers at older plants when they are modified.

Nearly 60 percent of facilities affected by the federal proposal probably won't be required to make any changes, according to EPA documents. Agency officials are taking public comments until July 16 and expect to finalize the rules by July 2012.

"This proposal is a big disappointment — a punt to states that have neither the expertise nor the political will to take this on effectively," said Thomas Cmar, an attorney with the Natural Resources Defense Council.

State regulators say they are doing the best they can with insufficient resources and conflicting guidance from federal officials. The EPA declined requests for interviews with Administrator Lisa Jackson or other top officials, but in response to written questions, the agency said its proposal "establishes a strong baseline level of protection and then allows additional safeguards for aquatic life to be developed through a rigorous site-specific analysis."

Bombarded for decades by industrial pollution and threatened by invasive species that aggressively compete for food and spawning grounds, many key species of fish in the lakes have been declining for years. In Lake Michigan alone, the estimated biomass of prey fish dropped to 30,000 tons in 2008, down from 450,000 tons a decade earlier.

Biologists, fishing organizations and environmental groups are focusing on Lake Erie because it supports more consumable fish than the other Great Lakes combined. More than half of those fish are in the lake's western basin where the Bay Shore and Monroe power plants are located.

Studies show the number of walleye in the lake dropped to 20 million last year from 80 million in 2004. The population of yellow perch has fallen so rapidly that commercial fishing operations have been banned from catching them in the western basin for three years.

"Fish populations are affected by a number of factors, but these power plants just make the situation worse," said Roger Knight, a biologist at the Ohio Department of Natural Resources. "I'd prefer they go to cooling towers and take care of their contribution to the problem once and for all."

Sandy Bihn, Lake Erie representative for the Waterkeeper Alliance, an environmental group, noted that state laws limit how many fish anglers can take out of the lakes, but many power plants face no restrictions on the numbers of fish they kill. "You and I would go to jail if we did something like this," she said.

In addition to daily catch limits, states try to stabilize game fish populations by stocking the lakes with salmon, trout, walleye and other species. Michigan, the state with the most Great Lakes shoreline, spends $7 million a year on fish stocking; Wisconsin spends $3 million and Illinois about $400,000 annually.

The total impact of power plants on the lakes is difficult to assess, in part because records examined by the Tribune show that fish kills at some plants haven't been researched since the 1970s. At some plants studied more recently, fish sucked into cooling intakes were counted for a few months and the sum was used to calculate annual estimates. Others used a complicated formula to determine how fish kills affect yields from sport and commercial fishing.

Analysts hired by government regulators and environmental groups also have questioned the reliability of industry estimates, suggesting they might be too low.

Consultants hired by energy companies have estimated that the vast majority of fish sucked into cooling intake screens, or impinged, are forage species like gizzard shad and emerald shiners or invasive species such as alewives and round goby.

"The relevant fact here is that the fish affected by our water intake structures … are almost entirely alewives that are dead or nearly dead when they wash into our intakes, while sport fish account for less than two-tenths of 1 percent," said Doug McFarlan, spokesman for Midwest Generation, the company that owns the Waukegan coal plant.

However, alewives and other smaller fish provide the base of the food chain for game fish.

The EPA was required to address the water-intake issue under a 2007 federal appellate court decision that threw out industry-friendly changes to the Clean Water Act made by the Bush administration. The decision, written by Sonia Sotomayor, now a U.S. Supreme Court justice, favored cooling towers as the most effective way to protect marine and freshwater ecosystems.

Since the decision, a Massachusetts nuclear plant has agreed to spend $620 million installing the structures under a settlement with the federal and state EPAs that is intended to help restore Mt. Hope Bay, an Atlantic Ocean estuary. Chicago-based Exelon recently decided to close a New Jersey nuclear plant by 2019 — 10 years earlier than planned — rather than install cooling towers demanded by state regulators as part of an effort to protect another Atlantic estuary.

Other states also are taking action. Last year, California adopted stringent rules that will require power plants along the Pacific Ocean to install cooling towers. New York denied a new permit for a nuclear plant on the Hudson River after concluding its once-through cooling system kills too many fish.

While the issue remained in legal limbo, state officials in Wisconsin allowed two power plants on Lake Michigan to skip installing cooling towers when they were overhauled during the past decade. "We made these decisions using our best professional judgment," said Paul Luebke, a permit writer for the Wisconsin Department of Natural Resources.

Instead, a plant in Port Washington built a porous dike in the lake designed to prevent fish from being sucked into the cooling intake. The other plant, south of Milwaukee in Oak Creek, will draw as much water from the lake every day as Chicago does — 2.2 billion gallons — but will do so through a "wedge wire" system of intakes covered with fine screens.

We Energies, the company that owns both plants, predicts the systems will save 90 percent of the organisms that used to be killed, though that has yet to be proved. Both are designed to draw water at less than a half-foot per second, slow enough for most fish to escape.

As part of a legal settlement with the Sierra Club and other groups, the company also will pay $4 million annually for the next 24 years to fund projects that improve Lake Michigan.

"The problem isn't the same at every one of these plants, and some companies have done a good job trying to reduce the impact," said David Jude, a University of Michigan biologist who has studied the Great Lakes for decades. "But some of these power plants were built in the worst possible places."

The Office of the Great Lakes has released the 2012 Michigan Water Conservation and Efficiency Program Review, which assesses Michigan’s progress in meeting its obligations under the Great Lakes–St. Lawrence River Basin Water Resources Compact.